A week after the Indianapolis Colts’ defense ended a disturbing trend by forcing four turnovers against the Tennessee Titans, it had an underwhelming performance in Sunday’s loss to at Cincinnati.

In the win over the Titans, the Colts gave up only 14 points — the fewest they’d allowed since a 37-3 win at Jacksonville in Week Four. But the flood gates reopened against the Bengals, who piled on points in a 42-28 win.

“I think we’ve played good in spots,” Colts coach Chuck Pagano said Monday. “You look (back) a couple ballgames ago, (defense) won the game for us.”

Turns out, the opposite was true against the Bengals.

The Colts gave up 430 yards, second only to the season-high 483 the Colts yielded on November 3 at Houston. Of particular concern were the Bengals’ big plays rushing and passing.

Bengals quarterback Andy Dalton, coming off an unsightly four-game stretch in which he threw six touchdowns and nine interceptions, carved up the Colts secondary with in a 275-yard, three-touchdown performance.

For the Colts, who clinched the AFC South title when the Titans fell to Denver late Sunday afternoon, the postseason will bring similar challenges. They are challenges the Colts haven’t consistently proved capable of withstanding.

“In the playoffs, the old cliché is that if you don’t have a quarterback, you don’t have a chance,” outside linebacker Robert Mathis said. “All teams (in the playoffs) have a good quarterback. We have one too so we have to help him and give him a chance to lead us.”

Mathis, the NFL’s sack leader, routinely is the center of attention from the opposing offensive front. But he made barely a ripple Sunday. He did not register a sack and barely came within shouting distance of Dalton, who was not sacked. It marked the first time this season the Colts failed to take down a quarterback, allowing Dalton more than ample time to throw to his many talented receivers.

But the Colts had equally distressing issues in the secondary, where cornerbacks Vontae Davis and Darius Butler, along with safety LaRon Landry, had forgettable games.

Davis and Butler, in particular, struggled. The defensive backs were often step for step with receivers but the receivers still managed to catch deep balls from Dalton. The Colts needed someone to make plays on the football, and that rarely happened.

The Bengals’ first touchdown, a 29-yard strike from Dalton to Marvin Jones, came with Davis in coverage, a half-step behind his man. But Davis never turned and found the football, allowing Jones to catch Dalton’s pass. The same thing played out with Butler in other instances.

“Personally, I know I can play better,” Butler said. “There are plays we left out there that we can do better on.”

The defense “made (those plays) two weeks ago,” Pagano said, referencing the Titans game. “We got four turnovers, three interceptions. So, we had guys in position to do the same thing (Sunday). You have to do it on a consistent basis.”

The Bengals’ passing game gained momentum while the Colts’ defense folded. Take the first possession of the third quarter, for instance. Dalton, in four plays, effortlessly connected on completions of 22, 16 and 15 yards.

Meanwhile, the Colts’ secondary was flagged for four penalties, including two against Davis (for pass interference and a questionable defensive holding). Landry missed several tackles, took poor angles and was a step late with help over the top of receivers on key plays.

“He had an opportunity on some of those balls that were thrown down the field,” Pagano said.

All 11 defenders can share in the blame when it comes to the running game. Rookie running back Giovani Bernard found little resistance as he rushed for 99 yards on 12 carries — 8.3 yards per carry. And Bernard did it with a long run of only 20 yards, benefitting from his offensive line’s surge against the Colts’ front seven.

So, with the playoffs approaching, the Colts defense has plenty to prove. Sunday’s loss demonstrated in vivid detail what defensive underperformance can mean against playoff-caliber offenses.